An autonomous device requiring a continuous and very low level of electrical power is generally provided with an internal electrical power source such as a battery, to supply the required power. Whilst the storage and discharge properties of the battery are selected to be appropriate for the device, such batteries do not always provide the anticipated amount of current or power before becoming depleted. This makes it difficult to ensure a reliable duration of the power source. Whilst the battery may be over-specified in an attempt to alleviate this, such a solution is not ideal and will not always resolve the problem.
One of the aims of the present invention is to improve the reliability and/or increase the duration of this kind of power supply, so as to reduce the intervention needed for an autonomous device that is powered therewith.